Light-emitting devices including a light-emitting element placed on a lead frame and a light-transmitting resin covering the light-emitting device and part of the lead frame are widely used as a variety of light sources. Such a light-emitting device has a possibility of causing variations in light distribution due to deterioration over time (variations due to changes in light distribution) in addition to initial variations in light distribution resulting from a configuration of a light-transmitting resin or a lead frame, light distribution characteristics of a light-emitting element or a gloss level of lead frame plating.
Heat generation of the light-emitting element in mounting the light-emitting device on a substrate or using (lighting) the light-emitting device is thought to be a major cause for variations in light distribution due to deterioration over time, and specifically, there are the following two cases for this. One results from the deterioration of a light-emitting element due to thermal stress and the other one results from peeling between the lead frame and the light-transmitting resin due to heat or light.
In order to address variations in light distribution over time due to such a thermal stress, JP-A-2002-353518 proposes light-emitting device in which an internal stress is relaxed and stress exerted on the light-emitting element is reduced by lowering adhesiveness between the lead frame and the light-transmitting resin material to prevent the deterioration of the light-emitting element. This light-emitting device has the effect on variations in light distribution resulting from deterioration of the light-emitting element due to a thermal stress. However, this light-emitting device cannot prevent variations in light distribution from occurring, since peeling partially occurs due to heat or light in a region where the lead frame is in contact with the light-transmitting resin to cause a situation in which there is a mixture of a contact area and a peeled area of between the light-transmitting resin and the lead frame. Further, since a light-transmitting resin having low adhesiveness is used in order to suppress thermal stress, there is a possibility that water or flux enters inside from the gap between the lead frame and the light-transmitting resin to corrode the light-emitting element or the lead frame.
JP-A-H11-103097 and JP-A-2004-88002 disclose prevention of water or flux from entering inside from the gap between the lead frame and the light-transmitting resin. In JP-A-H11-103097 and JP-A-2004-88002 propose to add a member for enhancing the adhesiveness between the lead frame and the light-transmitting resin at an end of the light-transmitting resin where the lead frame is exposed. In this case, it is necessary to add a sealing member other than the light-transmitting resin material and therefore there is a possibility that man-hour of manufacturing and production cost may increase.